The present invention is related generally to the field of medical methods and devices. More particularly, the present invention is related to the oral delivery of substances concurrently with the realignment of teeth.
Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning is accomplished by applying gentle controlled forces to the teeth over an extended period of time. Due to the limited space within the oral cavity and extensive movements that some teeth must undergo, the teeth will often be moved throughout a series of intermediate patterns to properly arrange the teeth. For example, molars may be temporarily moved backwards (distalized) to create adequate space for movement of the incisors. Thus, a single patient may experience an average of 25-30 stages or alignment patterns before achieving the final desired configuration.
Recently, it has been found that such repositioning may be accomplished with the use of a series of removable elastic positioning appliances. Such appliances comprise a thin shell of elastic material that generally conforms to a patient""s teeth but is slightly out of alignment with an initial or immediately prior tooth configuration. Placement of the elastic positioner over the teeth applies controlled forces in specific locations to gradually move the teeth into the new configuration. Repetition of this process with successive appliances comprising new configurations eventually move the teeth through a series of intermediate configurations or alignment patterns to a final desired configuration. A full description of an exemplary elastic polymeric positioning appliance is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present application. Both these documents are incorporated by reference for all purposes.
In addition to their ease of use, polymeric positioning appliances are generally transparent and impart substantial force on the teeth, due to stiffness of the appliance. The stiffness of an elastic positioning appliance is a result of the modulus of the thermoformable polymer materials from which it is made. The higher the modulus of the materials, the higher the stiffness of the appliance. When a patient positions such an appliance over a prescribed group of teeth, one or more of the teeth will provide a base or anchor region for holding the positioning appliance in place while the stiffness of the polymeric material will impart a resilient repositioning force against one or a portion of the remaining teeth. By designing the appliance to cover the teeth, a much larger contact surface area is afforded compared to traditional spring retainers and wire-based appliances.
As described, the appliances are only effective in repositioning teeth when the appliance is placed over the patient""s teeth. Removal of the appliance for any reason interrupts the treatment plan and lengthens the overall period of treatment. Therefore, removal of the appliance should be minimized for effective and timely treatment. However, a number of dental and periodontal therapies which may be desired or required by the patient may not be effectively utilized while the appliance is in place. Such therapies may be prescribed by a practitioner to improve oral health or they may be requested by the patient for cosmetic purposes.
Oral health concerns often include tooth decay, gingivitis, and periodontitis, to name a few. Tooth decay may be largely prevented or arrested with fluoride treatment. Treatments include toothpastes, gels, rinses and varnishes. Gum disease, such as gingivitis or periodontitis, is caused by bacterial growth associated with dental plaque and calculus deposits. The most common recommendation for preventing such bacterial growth is to mechanically remove the plaque from the tooth surfaces. However, chronic gingivitis and tooth decay have plagued many individuals who in fact comply with good oral hygiene methods and plaque removal. This may be due to a variety of factors including genetic predispositions, illnesses, mouth breathing, and medical treatment programs.
In such cases, bacterial control may be accomplished with the use of antibacterial drugs. A common antibacterial agent shown to be effective in reducing the activity of many common strains of oral flora is chlorhexidine. Chlorhexidine is a cationic biguanide microbicide with a broad spectrum of activity against many forms of bacteria and fungi. Therefore, it has been a popular agent in many studies of gingivitis reversal. Chlorhexidine has traditionally been delivered to the oral environment through the use of rinses, such as Peridex(copyright) (Proctor and Gamble). Sustained delivery to the gingiva has also been attempted with the use of chlorhexidine impregnated dental floss and dental appliances, such as trays or mouthguards.
Another frequently prescribed antibacterial agent is tetracycline. Tetracycline is a broad spectrum antibiotic which is effective against virtually all common groups of pathogenic bacteria, both gram positive and negative. Tetracycline may be combined with an antifungal agent, such as amphotericin, to provide activity against fungi. Tetracycline has traditionally been delivered to the oral environment through systemic administration, although localized delivery has been attempted with the insertion of tetracycline-filled hollow fiber devices into periodontal pockets and the use of tetracycline laden dental appliances, such as trays and mouthguards. In addition, a number of other antibacterial drugs are available for dental and periodontal therapy.
Cosmetic treatments often include tooth bleaching or whitening and breath freshening products. Discolorations of enamel and dentin may occur due to aging, consumption of staining substances (coffee, tea, colas, tobacco), trauma, staining due to systemic tetracycline (antibiotic) therapy, excessive fluoride, nerve degeneration and old dental restorations. Bleaching lightens these discolorations for a whiter or brighter appearance. Typically, a bleaching gel is placed in a thin custom-fitted tray that fits over the teeth. The tray is worn at night for usually 10 to 14 days and may require periodic re-bleaching treatments for approximately one or two nights every six months. Breath freshening products are often used by patients to treat halitosis or for enjoyment of the taste. These include a variety of sprays, rinses, mints, gums, or candies, to name a few.
Many of these therapies require access to the teeth and gingival margin which are typically covered by the elastic repositioning appliance when in use. In addition, some of these therapies may best be administered by localized delivery over extended periods of time which would create substantial interruption of the treatment plan. For example, low level delivery of antibiotics by sustained release methods is often desired to treat periodontal disease. Likewise, treatments such as bleaching and whitening may require interruption of the treatment plan for up to two weeks. Removal of the appliance during these periods would lengthen the overall treatment period. In addition, many of these therapies require the usage of specific devices, gels, rinses, applicators and instructions for each administration of therapy. These accessories may be costly, bulky and difficult to use.
Although removal of the appliance should be minimized, it is necessary to remove the appliance during daily oral hygiene routines, such as brushing and flossing of the teeth. Likewise, the appliance may be removed from time to time for participation in athletic activities or for comfort, such as when eating. The ability to temporarily remove such appliances allows the patient to pursue conventional oral hygiene, but teeth which are covered by the appliances a majority of the time may still be at an increased risk of dental and periodontal disease.
It would be desirable to provide improved devices, systems and methods utilizing elastic repositioning appliances which permit and/or enhance concurrent dental and periodontal therapies. Likewise, it would be desirable to provide such devices, systems and methods which would reduce or eliminate the need for additional accessories and/or protocols to apply such therapies. Further, the devices, systems and methods should be economical and easy to use. At least some of these objectives will be met by the designs and methods of the present invention described hereinafter.
The present invention provides devices, systems and methods for orthodontic treatment using repositioning appliances, typically elastic polymeric shells, while concurrently delivering substances to the teeth or gums, for example, to provide dental and periodontal and/or cosmetic therapies. Such therapies are traditionally provided with the use of a variety of accessories and devices which are applied using separate appliances, materials, etc. The present invention eliminates the need for such additional devices by incorporating these therapies into the repositioning appliance. Moreover, the ability to deliver therapeutic and other agents is concurrent with the course of a repositioning procedure.
By xe2x80x9cconcurrentxe2x80x9d or xe2x80x9cconcurrently,xe2x80x9d it is meant that the substance or agent delivery to the teeth occurs during at least a portion of the duration of the repositioning of the teeth. Thus, the substance may be delivered continuously during the entire duration of the repositioning process, i.e. the substance may be present in or on each repositioning appliance in an amount or amounts sufficient to assure that it is released to the oral environment at all times the appliance is placed over the teeth. Alternatively, the substance may be present in or on the repositioning appliance(s) at only selected times or over selected time intervals so that the substances are delivered at spaced-apart times during the repositioning process. For example, each successive repositioning appliance may be preloaded with a bolus of the substance so that the bolus is delivered to the patient at the outset of use of each new appliance. After the initial bolus is depleted, the substance will not be delivered again until the next successive appliance is used. As an alternative example, the patient could apply an amount of a substance at a time each day, where the substance is then released over a relatively short time interval and no more substance delivered until the next day. A multitude of other particular patterns are also possible.
While the appliances will be particularly intended for repositioning teeth, most often when used in systems of multiple aligners, t hey may in some instances be useful as drug or substance delivery devices without the concurrent repositioning of teeth. In particular, many of the specific device constructions described below are themselves novel and useful for substance delivery, and the present invention encompasses such devices.
In a first aspect of the present invention, an oral delivery appliance comprises an elastic repositioning appliance providing one or more substances or agents for oral delivery. As previously described, elastic repositioning appliances comprise a thin shell of elastic polymeric material having cavities shaped to receive and resiliently reposition teeth from one arrangement to a successive arrangement. This is possible because the cavities are shaped to fit a mold of digitally arranged teeth in the successive arrangement. A full description of an exemplary elastic repositioning appliance shaped in this manner is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596. Placement of the elastic positioner over the teeth applies controlled forces in specific locations to gradually move the teeth into the new configuration. In order to apply sufficient force, the appliance generally covers the tooth surfaces and portions of the gingival margin. Thus, both individual repositioning appliances and systems of such elastic repositioning devices may be used to deliver agents to the underlying tooth surfaces and gingiva comprising the oral environment while repositioning teeth.
In a first embodiment, the oral delivery appliance delivers fluoride to the oral environment to prevent or treat tooth decay. Traditionally, fluoride has been delivered to the oral environment through the use of toothpastes, gels, rinses and varnishes, to name a few. The present invention provides fluoride delivery which may be used in conjunction with traditional applications or may replace certain applications. Such fluoride may be provided in a number of forms, such as neutral sodium fluoride, stannous fluoride, hydrogen fluoride, or acidulated phosphate fluoride (APF) gel, for example. Fluoride may be releasably attached to the elastic repositioning appliance in a number of forms, as will be described in more detail in later sections, to provide delivery to the oral environment.
In a second embodiment, the oral delivery appliance delivers an antibiotic or drug to the oral environment. In the case of antibiotics, delivery of such an agent may inhibit or kill various microorganisms. Antibiotics often used to treat gingivitis and periodontitis include chlorhexidine and tetracycline. Such antibiotics may be releasably attached to the elastic repositioning appliance in a number of forms, as will be described in more detail in later sections, to provide delivery to the oral environment.
In a third embodiment, the oral delivery appliance delivers a bleaching material to the oral environment. Bleaching of the teeth is a common cosmetic procedure requested of dental practitioners by their patients. The active ingredient in standard bleaching gels is carbamide peroxide and is typically present in an 18-37% suspension. Bleaching materials, such as carbamide peroxide, may be releasably attached to the elastic repositioning appliance in a number of forms, as will be described in more detail in later sections, to provide delivery to the oral environment.
In a fourth embodiment, the oral delivery appliance delivers a breath freshener to the oral environment. Breath fresheners are commonly available in a number of flavors and scents, including mint and fruit flavors, derived from essential oils and/or natural or artificial flavorings, to name a few. Such breath fresheners may be releasably attached to the elastic repositioning appliance in a number of forms, as will be described in more detail in later sections, to provide delivery to the oral environment.
In a second aspect of the present invention, at least some of the elastic repositioning appliances in a system for repositioning teeth are coupled to means for releasing the agent to the oral environment when the appliance is placed over the teeth. Such means may comprise a layer which includes the agent. The layer may be formed over at least a portion of the surfaces of the repositioning appliance. These surfaces include both the cavity surfaces, the surfaces within the cavities which contact the teeth when in place, and the external surfaces, the surfaces of the appliance which contact the cheeks and lips when in place. The layer may be comprised of various materials and may take a variety of forms. For example, the layer may consist essentially of the agent. In other words, the agent may be attached directly to a surface of the polymer shell of an elastic repositioning appliance. This may be achieved by applying the agent (optionally in an inert carrier or diluent) itself to the surface utilizing a number of methods, such as spraying, painting and/or dipping. When the repositioning appliance is placed over the patient""s teeth, the agent may then be released to the oral environment.
Alternatively, the layer may comprise the agent present in or on a carrier or binder which promotes adhesion or attachment to the appliance and/or which creates a matrix from which the agent can be released by diffusion or dissolution. In one embodiment, the agent is dissolved in the carrier or binder. In this case, the agent may be provided in powder or similar form and dissolved in a liquid solvent. The result may be a solution which may be applied to a surface of the shell, typically by spraying, painting and/or dipping, to form a coating or film. When the repositioning appliance is placed over the patient""s teeth, the agent may then be released from the coating to the oral environment. Release may be due to activation or deactivation of the carrier or any other releasing mechanism, such as by enzymes or proteins in saliva. Or release may be due to degradation of the carrier by contact with, for example, saliva. In some cases, the binder or carrier may evaporate upon application to the layer to the surface leaving the agent behind. In these cases, the agent may be released in a similar fashion as when the agent is directly attached to the surface, as described above. It may be appreciated that any agent, particularly fluoride materials, antibiotics, bleaching materials and breath fresheners, may be delivered to the oral environment in this manner.
In another embodiment, the agent is encapsulated or suspended in the layer. A common material for suspension of an agent is a semisolid material, such as a gel, jelly or putty. Such a material may be applied to a surface of the shell by spraying, painting and/or dipping to form a coating or film. Here, as in all cases, suspension is not limited to a scientific definition and may refer to any situation in which a carrier holds, contains, supports or otherwise includes an agent. Alternatively or in addition, the semisolid material may be deposited in the cavities of the polymer shell which are shaped to receive the teeth. The cavities may be filled to any desired level. When the repositioning appliance is positioned over the teeth, the teeth will directly contact the semisolid material in the cavities and displace any extra material as the teeth are inserted into the cavities. Therefore, it is desired to fill the cavities to a level which will avoid excess overflow of the material from the appliance. Delivery of an agent by use of a semisolid suspension material is common in bleaching treatments and fluoride treatments, for example. However, such treatments apply the material with the use of a tray or generic appliance which does not apply repositioning forces to the teeth. By modifying a repositioning appliance, as described above, orthodontic treatment may continue throughout the delivery of such agents. It may be appreciated that any agent, particularly fluoride materials, antibiotics, bleaching materials and breath fresheners, may be delivered to the oral environment in this manner.
Another common material for encapsulation or suspension of an agent is a controlled-release material. Thus, the layer may be comprised of a rate-controlling material wherein the rate controlling material controls the rate at which the agent is released from the layer. Controlled-release or rate-controlled materials deliver a predetermined amount of an agent at a predetermined rate. Often such delivery maintains a steady-state concentration of an agent in an environment within a desired therapeutic range for a prolonged period of time. Thus, a prescribed dosage may be delivered. In addition, the ability to sustain delivery eliminates the need for repeated applications of the agent for dosed delivery to the oral environment.
Although such controlled release materials may be provided as a semisolid material, such as a gel, jelly or putty, as described above, these materials may also be provided as a solid material which is attached to the polymeric shell of the repositioning appliance. One type of controlled-release material comprises a polymer matrix membrane within which finely dispersed particles of an agent are suspended. The agent may diffuse through the matrix membrane according to a concentration gradient. Alternatively or in addition, the agent may be released by degradation of the polymer matrix membrane material. In either case, the controlled-release material may be provided as a sheet which may be laminated to a surface of the shell. The controlled-release sheet may be layered with the elastomeric polymer and vacuum formed over a mold to form the repositioning appliance. The controlled-release material may be arranged so that it is present on the inside or outside surfaces of the appliance depending on the material and desired application. Or, the controlled-release sheet may be laminated or bonded to a surface of the polymeric shell after forming to supply agent delivery in desired areas. Alternatively, the controlled-release material may be provided as a tablet or similar mass which may be inserted into the polymeric shell of the repositioning appliance. The agent may then elute from the tablet into the oral environment over time.
In another embodiment, the agent may be held within pores of a material and may elute out at a controlled rate from the pores. The agent itself may be absorbed into the pores of the material, or the agent may be suspended in a carrier which is absorbed into the pores of the material. In the latter case, the agent may be released from the carrier by diffusion and/or by controlled degradation of the carrier material. This may incorporate a rate-controlling mechanism in addition to the controlled-release of the agent from the pores. As mentioned, in some cases, enzymes in the patient""s saliva will activate the release or degrade the carrier material to release the agent. It may be appreciated that the agent may be released by a combination of any of the release methods.
In a further embodiment, the polymeric shell of the repositioning appliance itself comprises a controlled-release material containing the agent. In this case, at least a portion of at least some of the polymeric shells in a system for repositioning teeth are formed from a controlled release material wherein the rate controlling material controls the rate at which the agent is released from the shell. As previously described, the controlled-release material may be a provided in the form of a sheet. Thus, the sheet of controlled-release material may be vacuum formed over a mold of the patient""s teeth to form a repositioning appliance itself. In this manner, no additional elastomeric materials may be needed to form the appliance. The controlled-release material may be a polymer matrix membrane, a porous material or any suitable material. Controlled-release may be designed so that the elution rate of the agent corresponds to the repositioning rate of the teeth. The agent may elute throughout the repositioning process, concluding as the teeth reach the desired arrangement prescribed by the appliance.
In a still further embodiment, the releasing means coupled to at least some of the repositioning appliances comprises a reservoir formed in the shell of the appliance in addition to the cavity which receives the teeth. Typically, a rate controlling membrane is disposed over the reservoir wherein the rate controlling membrane controls the rate at which the substance is released from the reservoir. The reservoir may be pre-filled or pre-loaded with an agent or substance for delivery. In this case, the appliance may be ready for insertion or use upon removal from any packaging without the need of loading the appliance with the agent for delivery. If the releasing means is designed for a single delivery period, the appliance may be worn throughout the prescribed repositioning period and then disposed of. If the releasing means is designed for multiple delivery periods, the reservoir may be replenished with the agent to be released any number of times throughout the prescribed repositioning period. It may be appreciated that any agent, particularly fluoride materials, antibiotics, bleaching materials and breath fresheners, may be delivered to the oral environment in this manner.
In some instances, it may be desirable to change a visual characteristic of the polymeric shell of an oral appliance. Such appliances comprise a polymeric shell having a cavity shaped to be removably placeable over the teeth and a material on or within the shell that changes a visual characteristic of the shell. Such a change is typically in response to a change in the environment. In some cases, the visual characteristic is a color, such as green, red or blue. Thus, the appliance may appear colored or a particular color under certain environmental conditions, either in the oral environment or when removed. The described material may be a dye which changes color in response to a change in temperature. For example, the dye may change color when the appliance is removed from the mouth and changes temperature from body temperature (37xc2x0 C.) to room temperature (25xc2x0 C.). Similarly, the dye may change color when the appliance is rinsed with cool water.
In a fourth aspect of the present invention, methods for concurrently repositioning teeth and delivering agents to the oral environment of a patient are provided. For example, one method comprises placing a first tooth position adjustment appliance over the patient""s teeth, wherein the teeth move to a first tooth arrangement. After removal of the first appliance, a second tooth position adjustment appliance is placed over the patient""s teeth wherein the teeth move to a second tooth arrangement. Concurrently with the repositioning of the teeth, an agent or substance is released from at least one of the first and second tooth position adjustment appliances to the oral environment while the appliance is in place of the patient""s teeth.
Although the appliance may be pre-loaded with the agent and ready for use upon removal from any packaging, appliances that are not pre-filled or pre-loaded may require loading prior or immediately prior to placing the appliance over the teeth. Loading may comprise placing the agent in a teeth-receiving cavity. As described previously, the cavities may be filled to any desired level. When the appliance is positioned over the teeth, the teeth will directly contact the agent in the cavities as the teeth are inserted into the cavities. Alternatively, loading may comprise placing the agent into an agent release reservoir in the appliance immediately prior to placing the appliance over the teeth. The agent will then elute from the reservoir into the oral environment when the appliance is in place over the teeth. The elution rate may be controlled by a controlled release membrane which separates the reservoir from the surrounding environment. Loading may also comprise adhering a rate controlling material containing the agent to a surface of the appliance prior to placing the appliance over the teeth. Such a material may comprise a polymer matrix membrane which may be removably or permanently adhered to the polymeric shell of the appliance in desired areas for delivery of the agent. And finally, loading may comprise absorbing the agent into a porous material on or within the appliance immediately prior to placing the appliance over the teeth.
Repositioning of the teeth with the use of a position adjustment appliance involves placing the appliance over the teeth. However, the appliance is periodically removed for daily dental hygiene practices and other events throughout the repositioning protocol until the teeth are moved to at least near the desired tooth arrangement. While the appliance is removed from the teeth, the appliance may be replenished with the agent or substance for delivery. Replenishment may be performed immediately prior to each time the appliance is replaced over the teeth or it may be performed according to any prescribed protocol.
In a fifth aspect of the present invention, methods for introducing agent delivery to a prescribed tooth repositioning treatment plan are provided. A treatment plans is determined by an orthodontist or practitioner at the outset of orthodontic treatment. The plan involves moving the teeth through a series of intermediate configurations or arrangements to a final desired arrangement with the use of a system of tooth positioning appliances. Each appliance comprises a polymeric shell having cavities which is removably placeable over the teeth and wherein the cavities of successive shells are shaped to reposition teeth from one arrangement to a successive arrangement according to the treatment plan. The entire series of appliances may be provided at the outset of treatment, or a subset of appliances. In any case, the need or desire for delivery of an agent to the oral environment may occur at any point during the course of treatment. In such a case, an agent and/or means for releasing an agent to the oral environment may be coupled to an appliance at any time during treatment.
Means for releasing the agent may include a number of embodiments, including any such means previously described. Typically, means for releasing the agent comprises a layer including the agent, as previously described, and coupling comprises adhering the layer to at least a portion of a surface of the appliance. When the layer consists essentially of the agent, adhering may involve coating, spraying, dipping or painting the agent on the surface of the appliance. Thus, a pre-formed appliance may simply be coated with the agent prior to insertion in the patient""s mouth. When the layer comprises an agent present in or on a carrier or binder, adhering may involve attaching the carrier or binder a surface of the appliance. Similarly, when the agent is encapsulated in the layer, the layer may be attached to the surface of the appliance. The layer may comprise a sheet of rate controlling material wherein the rate controlling material controls the rate at which the agent is released from the layer. In this case, the sheet may be bonded to the surface of the appliance with an adhesive. Alternatively, the sheet may be attached to the surface by press fitting. The sheet and the surface may each be shaped so that they snap or fit together by pressing them together. For example, the sheet may have a formed protrusion and the surface a formed inset, wherein the protrusion fits into the inset when pressed upon the inset and holds the sheet in place. In many instances, the appliance may be porous or have a reservoir which can be loaded with a desired agent at any time the treating professional and/or the patient decide that it is appropriate. For example, an appliance can be immersed in a solution f the agent, allowing the appliance to absorb or adsorb the agent at a particular time.
In addition, the sheet may be pre-formed to a shape adapted for fitting against the surface of the appliance or a surface of the teeth or gingiva. For example, the sheet may be pre-formed to reflect the shape of the surface of one or more teeth or the gingiva, particularly along the gingival margin. The preformed sheet may then be held against that surface when the sheet is coupled to the appliance and the appliance is placed over the teeth. Coupling may involve any means of attaching the sheet to the appliance. In particular, the pre-formed sheet may further comprise an adhesive layer which may provide bonding of the sheet to the surface of the appliance.